1. Field of the Invention
The present invention generally relates to devices for preventing electrostatic discharge, and more particularly to a wristband having two separate conductive paths therein, the wristband and conductive paths being connected to a conductive grounding tether having two wires.
2. Description of the Prior Art
Electrostatic discharge, as well as the mere presence of a static electric field, can be extremely detrimental to sensitive electronic parts. This is particularly true of modern semiconductors and integrated circuits which may be degraded or destroyed by the buildup of static electricity in the workplace. Especially sensitive components can be severely affected by an electrical potential as small as 50 volts, yet the simple act of walking has been known to triboelectrically generate a potential of 30,000 volts or more.
The most common tool heretofore used in the battle against electrostatic discharge is a conductive tether which is designed to drain away excess electrostatic charge. One of the earliest grounding tethers is described in U.S. Pat. No. 3,015,754 issued to W. Legge, which illustrates a grounding strap for a human leg, with a tether connecting the strap to a conductive tread to be attached to the bottom of a shoe. Later devices incorporated a wrist strap, and several variations of the wrist strap and/or grounding tether are disclosed in numerous patents.
The subject invention relates to a wrist strap having two separate conductive pathways and, accordingly, the closest prior art is probably U.S. Pat. No. 4,639,825. Such a dual conductor wristband is useful in conjunction with systems which monitor the resistance of the grounding tether, for example, the system shown in FIG. 11 of Breidegam. In order to interface a dual conductor wristband with such a monitor, however, a two-wire tether is also necessary. In fact, the subject invention deals not so much with the wristband itself, but rather with the connection means between the dual conductor wristband and the two-wire tether.
Examples of two-wire tethers appear in several patents, viz., U.S. Pat. Nos. 4,605,984 (Fiedler), 4,638,399 (Maroney et al.), 4,639,825 (Breidegam), and 4,720,764 (Lucas). Unfortunately, each of the two-wire tethers disclosed in these patents suffers from serious drawbacks. For example, the tether disclosed in Fiedler is shorted at the distal end which is totally unacceptable for use with the type of monitor described in Breidegam. Maroney et al. depicts the use of a shielded cable whose conductors are similarly shunted at the distal end and hence likewise worthless for use with the present invention. The tether of Breidegam is essentially two separate tethers joined along the length of the wires with two snap connectors at the proximate end for connection to the wristband. The provision of two separate connectors, however, creates a problem for the wearer in that movements of the wrist, arm and hand may cause the two lines emanating from the snap connectors to become tangled up, possibly even causing one connector to become disconnected. Conversely, rotational interference between the two connectors may inhibit the dexterity of the wearer, which affects performance on the assembly line. Finally, the wires in the Lucas tether are shorted together at both ends, which is clearly unacceptable. It would, therefore, be desirable and advantageous to devise means for connecting a two-wire tether to a dual conductor wristband which would overcome the above-noted problems.
Accordingly, the primary object of the present invention is to provide a dual conductor wristband for drainage of excess electrostatic charge.
Another object of the invention is to provide such a wristband having a single female jack for connection to a two-wire grounding tether.
Still another object of the invention is to provide a two-wire grounding tether which cooperates with the movements of the individual wearing the wristband.
Yet another object of the invention is to provide a wristband which prevents accidental connection to a source of electrical potential.